Fort Worth daily gazette. (Fort Worth, Tex.) 1882-1891, 1887-05-02
IRON URYST4LLIzATION.
Changes In the Fibre of Metal Which 1t is
Impossible to Detect
Philadelphia Record.

Philadelphia Record.
Since q passenger train on the North
British Railway plunged from the great
iron bridge over the Firth of Tay into the
dark waters below, one stormy Deem
Der night seven years ago, carrying every
there has been no railroad bridge disaster
that has excited so much public atten-
ton as that which recently occurred on
the Boston and Providence Railroad at
the Bussey bridge, near Boston. In both,
the cause appears to have been struc-
tural defect. This may also be said of
the Ashtabula accident, whose horrors,
however, were increased by the fierce
work Of flames and the incIemencies of q
bitterly cold winter night.
Bridge accidents are considered by all
railroad men as imcomparably the worst
to which travel by rail is exposed, and as
among the most difficult to Q lard against
absolutely. One source of danger was
shown in last Wednesdays Record, when
the peculiar effects of a locomotives
hammer blows upon track were ex-
planned. The theory was advanced that a
girder Of the bridge had broken be-
meath the engines drivers, whose pound
ing upon the effectively constructed
bridge was thus primarily the cause of
the accident. This brings up phase of
railroad and bridge accidents which is at
present receiving great deal of Rtten-
ton. Capitalization in the material Oh
iron bridges is an element of danger now
so well recognized thst the Pennsylvania
Railroad Company has adopted the
definite policy of substituting stone for
iron bridges, and the same plan is being
followed by other railroad companies.
The lifetime of an iron bridge is from
twenty to twenty-five years, and constant
care is necessary to insure its safety. The
Ashtabula bridge was thirteen years old,
and at the time it fell beneath the weight
of two engines and heavy express train
the theory was commonly advanced that
crystallization had impaired its original
strength. The two great NOV
ing causes of crystallizstion are
Iteration and the hammer
blow of the locomotive, which gradually,
by repeated impact, turn the fibre of iron
or steel into 8 mass of crystals, needing
only some unusual pressure blow
to cause them to break apart. Add to
this the oscillation caused by the passage
of trains at high rate OF speed, and it
viii be seen that an iron bridge is exposed
to peculiar perils, which can only be
guarded against by rigid inspection and
constant renewals.
THE OPINION OF A DISTINGUISHED ENGI-
NEER.
Capitalization was one of the several
theories advanced by Park Benjamin,
New York engineer, to account for the
Tay bridge accident. He said:
General indications 60 to show that the
cause must be sought in an abnormal
condition of the structure, or rather one
which did not enter into the calculations
of the builders. Such condition would
be the deterioration of the metal by its
change from a fbrous to a crystalline
state under repeated vibration. That
this occurs in railway bridges has been
disputed By many well-known
engineers. On the other hand, many ex-
amples are quoted by different authori-
ties to support the theory. Apropos to
this particular accident, distinguished
French engineer and iron founder now in
this country informs Us that he has known